Still thinking inside the box, but I tihnk chalk is the best accessory. I cleaned an extra 10kg on monday and I'm sure half the reason was because my grip was absolutely rock solid.
I was also deadlifting on tuesdy and cos' I had no straps I tried hook gripping the bar. I could only get one rep at a time. I know this wouldn't have been a problem if I'd had chalk.
The other best accessory would have to be a gram of test a week!